1. Field of the Invention
The present invention relates to a flip chip test structure, and more particularly to a low cost flip chip test structure.
2. Description of the Related Art
FIGS. 1 and 2 respectively show two conventional flip chip wafer probe cards. As shown in FIG. 1, the flip chip wafer probe card comprises a probe card printed circuit board (PCB) 102 and a transformer 104. The printed circuit board 102 has circuits for transmitting signals from the transformer 104 to a test equipment (not shown). The transformer 104 is used as a signal distribution interface between the printed circuit board 102 and the tested chips. The transformer 104 has circuits therein and contacts on one side to transmit test signals to the printed circuit board 102. The transformer 104 has probes 106 which are used to contact input/output pads of the tested chips. The transformer 104 is replaceable and must be redesigned and manufactured for testing various kinds of chips. FIG. 2 shows another configuration of a conventional flip chip wafer probe card. The flip chip wafer probe card comprises a probe card printed circuit board (PCB) 202 and a transformer 206. The transformer 206 transmits test signals to the probe card printed circuit board 202 through contacts 204. The transformer 206 has a probe frame 208 used to contact input/output pads of the tested chips.
When the conventional flip chip wafer probe cards are used to test flip chip package dies, the probe 106 or the probe frame 208 contact with the pads of the flip chip package dies. The probe 106 or the probe frame 208 transmit test signals to the transformers 104 or 206 and the transformers 104 or 206 distribute signals to a bigger signal pitches which is suitable to requirements of PCB layout. The transformers 104 or 206 then transmit the bigger-pitched signals to PCB of the probe card.
However, the conventional transformer has several disadvantages. The conventional transformers are made of ceramic material and the manufacturing tooling costs are expensive. Moreover, since one type of transformer is usually designed and manufactured only for a certain chip and few number of the transformer are need, the cost of chip test is very high because the expensive tooling charge is divided by only few transformers.
Similarly, a probe card PCB needs to match a transformer very well so that either an interposer 103 or solder balls 204 can connect probe card PCB and transformer with good electrical performance. The design and tooling cost of probe card PCB is also expensive due to the same reason that only few probe card PCBs are made. The design, tooling cost and actual manufacturing few transformers and probe card PCB can be 5 to 10 times more expensive compared to conventional non-flip chip probe card. This adds burden to flip chip manufacturing in terms of break-even point.
In view of the drawbacks mentioned with the prior art flip chip test probe card, there is a continued need to develop new and improved flip chip test structures that overcome the disadvantages associated with prior art.